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Journal of Virology, February 2000, p. 2029-2037, Vol. 74, No. 4
Departments of Pathology and Molecular
Microbiology, Washington University School of Medicine, St. Louis,
Missouri 63110
Received 16 July 1999/Accepted 10 November 1999
Gene 50 is the only immediate-early gene that appears to be
conserved among the characterized gammaherpesviruses. It has recently been demonstrated for the human viruses Epstein-Barr virus (EBV) and
Kaposi's sarcoma-associated herpesvirus (KSHV) that ectopic expression
of the gene 50-encoded product in some latently infected cell lines can
lead to the induction of virus replication, indicating that gene 50 is
likely to play a pivotal role in regulating gammaherpesvirus reactivation. Here we demonstrate that the murine gammaherpesvirus 68 (
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of Gammaherpesvirus 68 Gene
50 Transcription
HV68) gene 50 is an immediate-early gene and that transcription of
HV68 gene 50 leads to the production of both spliced and unspliced forms of the gene 50 transcript. Splicing of the transcript near the 5'
end serves to extend the gene 50 open reading frame, as has been
observed for the gene 50 transcripts encoded by KSHV and herpesvirus
saimiri (Whitehouse et al., J. Virol. 71:2550-2554, 1997; Lukac
et al., Virology 252:304-312, 1998; Sun et al., Proc. Natl. Acad. Sci.
USA 95:10866-10871, 1998). Reverse transcription-PCR analyses, coupled
with S1 nuclease protection assays, provided evidence that gene 50 transcripts initiate at several sites within the region from bp 66468 to 66502 in the
HV68 genome. Functional characterization of the
region upstream of the putative gene 50 transcription initiation site
demonstrated orientation-dependent promoter activity and identified a
110-bp region (bp 66442 to 66552) encoding the putative gene 50 promoter. Finally, we demonstrate that the
HV68 gene 50 can
transactivate the
HV68 gene 57 promoter, a known early gene target
of the gene 50-encoded transactivator in other gammaherpesviruses.
These studies show that the
HV68 gene 50 shares several important
molecular similarities with the gene 50 homologs in other
gammaherpesviruses and thus provides an impetus for future studies
analyzing the role of the
HV68 gene 50-encoded protein in acute
virus replication and reactivation from latency in vivo.
*
Corresponding author. Mailing address: Departments of
Pathology and Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Ave., Box 8118, St. Louis, MO 63110. Phone: (314) 362-0367. Fax: (314) 362-4096. E-mail for Herbert W. Virgin: virgin{at}immunology.wustl.edu. E-mail for Samuel H. Speck:
speck{at}pathology.wustl.edu.
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